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Science Serving Maryland's Coasts

Barrett Wessel, University of Maryland, College Park

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Project Title: 

Factors Responsible for the Development of Fe Flocculate in Streams with and without Regenerative Stormwater Conveyance (RSC) Structures


A relatively new ecological engineering design developed to reduce stormwater runoff and pollutant loads is called a Regenerative Stormwater Conveyance (RSC). RSCs are implemented in degraded headwater streams using sand, woodchips, cobble, and ironstone boulders to create a series of stepped pool conveyance structures. Concern has been raised that RSCs exhibit excessive accumulations of flocculate mats created by iron-(Fe)-oxidizing bacteria. Iron sources and other factors responsible for mat formation are poorly understood, as well as how RSCs affect stream habitat and water chemistry. Leaching experiments were done on riparian soils and substrates used in RSC construction with and without added dissolved organic carbon (DOC) to identify Fe sources and the factors driving its release. Riparian and hyporheic ground- and surface-water chemistry, and physical habitat parameters, from six RSCs and three reference (control) streams in urban catchments of the Coastal Plain and Piedmont physiographic provinces of Maryland were compared. A longitudinal transect of one RSC was done to evaluate potential density changes of Fe-oxidizing bacterial mats and the solute composition of water in successive pools/riffles of the structure. This study suggests that both ironstone and riparian soils contribute to Fe bacterial mat formation, a process accelerated by the presence of DOC.

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PhD student at University of Maryland